Traditional incandescent light bulbs are currently being replaced by other light sources having higher energy efficiency and less environmental impact. Alternative light sources include light emitting diode (LED) devices and fluorescent light sources. However, LED devices are expensive and complicated to fabricate and fluorescent light sources are known to contain small amounts of mercury, thereby posing potential health problems due to the health risks involved in mercury exposure. Furthermore, as a result of the mercury content, recycling of fluorescent light sources is both complicated and costly.
An attractive alternative light source has emerged in the form of field emission light sources. A field emission light source includes an anode structure and a cathode structure, the anode structure consists of a transparent electrically conductive layer and a layer of phosphor coated on the inner surface of e.g. a transparent glass tube. The phosphor layer emits light when excited by the electrons emitted from the cathode structure.
Furthermore, it is known that nanostructures are suitable for use as the field emitters in a cathode structure. Several methods for fabricating nanostructures are known. As an example, Yang et al., Chin. Phys. Lett. Vol. 26, No. 3 (2009) 038101 discloses a method for fabricating ZnO nanoneedles for use as field emitters. However, the method disclosed by Yang et al. includes several process steps not suitable for large scale fabrication of field emission devices such as the high temperature growth step and the random distribution of nanostructures.
Accordingly there is a need for an improved method for fabrication of nanostructures for use as field emitters.